Field of the Invention
The invention generally relates to stage-specific Borrelia antigens for diagnosing, treating and/or preventing Lyme disease. In particular, the invention provides chimeric and recombinant mutant Borrelia antigen constructs, as well as multiprotein assays and vaccine preparations utilizing the constructs.
Background
Lyme disease, also known as Lyme borreliosis, is an infectious disease caused by several bacterial species belonging to the Borrelia burgdorferi sensu lato complex. This complex of bacteria consists of approximately 15 species. The word approximately is used in the previous sentence because the species status of some in the group has not yet been fully agreed upon by the research community. The major species that are associated with human and veterinary infections are B. burgdorferi, B. garinii, B. afzelii, and B. bavariensis. Collectively all bacterial species in the B. burgdorferi sensu lato complex are commonly referred to as the Lyme disease spirochetes. The Lyme disease spirochetes are transmitted to humans and animals through the bite of infected ticks of the Ixodes genus. Lyme disease is now the most common arthropod borne disease in the Northern Hemisphere. It is estimated to affect 300,000 to 600,000 people a year in the United States with similar numbers in Europe. While Lyme disease also occurs in parts of Asia the actual number of cases is not well defined due to difficulties in tracking cases. In North America, the primary species that causes disease in humans and companion animals is Borrelia burgdorferi (sometimes referred to as B. burgdorferi sensu stricto), while in Europe and Asia, at least four species cause Lyme disease (B. burgdorferi, B. afzelii B. bavariensis and B. garinii). Diagnosis of Lyme disease remains a controversial and difficult area. Currently, diagnosis is made based upon a combination of symptoms, history of tick exposure, and serological assays that test for antibodies to the bacteria in the blood.
Current diagnostic tests for Lyme disease are considered by public health authorities and the medical and research communities as being highly unreliable. In addition, the most commonly used commercially available tests are not able to detect early infection, distinguish between prior and active infection, or differentiate early and late stage disease. These are significant disadvantages since the optimal and most effective treatment strategies for early and late stage Lyme disease, particularly in humans, differ. Early stage disease is treated with oral antibiotics while intravenous antibiotics are used by most clinicians to treat late stage infection. Because currently available diagnostics do not distinguish between disease stages, patients with late stage disease are thus frequently subjected to multiple ineffective courses of oral antibiotics before receiving more effective IV treatment.
In addition, antigens currently used in Lyme diagnosis are typically native natural proteins, or peptides derived from those proteins. The proteins used in these assays are derived in most cases from a single strain of Lyme disease spirochete. The tests are not designed to detect the multiple species that can cause disease in humans or animals. In addition, proteins of the Lyme disease spirochetes have been demonstrated to vary considerably in sequence from strain to strain (even of the same species). Hence, the failure to consider this in assay design or use of proteins that are not evolutionary conserved can lead to false negative test results. To restate, few proteins produced by the Lyme disease spirochetes during natural infection meet the criteria of being highly conserved among the multiple species of bacteria that cause Lyme disease worldwide, and current tests do not employ a sufficient number of appropriate antigens to ensure detection of diverse strains.
There is a pressing need in the art to provide accurate diagnostic tests to detect Lyme disease infection. In particular, there is a need to accurately differentiate among different stages of Lyme disease so that appropriate treatment can be administered, and to detect the presence of infection caused by diverse Borrelia strains.